Definition 4 (Covering Number) [1]} Based on the notations in Def.REF , the covering number of \(\Theta \)  with radius \(\epsilon \)  is defined as:
\(\mathfrak {C}(\epsilon ,\Theta , d) = \min \left\lbrace n: \exists \epsilon -\text{covering over $\Theta $ with size n}\right\rbrace .\) 

